The present invention relates to improvements in very high-pressure, low-delivery liquid pumps particularly for waterjet cutting such as used in waterjet slitters for slitting a continual traveling web of paper.
Waterjet cutting is used in a variety of industries. It has been discovered that using a moving high-pressure stream of liquid for cutting affords advantages in that the liquid can be ordinary tap water without additives. The cutting operation is dust-free and does not create critical dust problems which result in creating wear in machinery, pollution of the air and health hazards. Waterjet cutting is advantageous in that it does not require space-consuming and complex cutting equipment, and the mechanism can be easily operated and controlled for a variety of cutting conditions with variations in speed and thickness of material and other variations which must be encountered in commercial cutting operations.
However, to provide a continuous supply of water in very small quantities at very high pressures such as used in paper web cutting, the reliable operating life of pumps now available is severely limited. Pressures in the range of 10,000 psi to 60,000 psi must be available at very small delivery quantities of water and such pumps frequently have a operating life on the order of only two hundred and fifty hours without requiring shut-down and attention. Further, such pumps require parts with critical tolerances and the moving parts must be carefully and precisely machined. Also, conventional pumps are generally mechanically very complex and many are unreliable in applications where the fluid is water and cannot contain rust inhibitors.
Accordingly, it is an object of the present invention to provide an improved pump for delivering a cutting fluid such as water in low volumes at very high pressures and is capable of doing so over long operating periods without attention to repair.
A still further object of the invention is to provide a very simplified pump structure requiring a minimum of moving parts and a minimum of machined parts with the parts not requiring critical tolerances for pumping liquid in very small volumes at very high pressures.
A still further object of the invention is to provide an improved rotary high-speed, high-pressure pump wherein the output pressure can be easily and readily controlled during operation, and where the number of contacting parts are reduced to a minimum to reduce operating wear.
A further object of the present invention is to provide a high-speed rotating high-pressure pump which is capable of an almost indefinite operating life because of the absence of contacting wearing parts.
Other objects, advantages and features will become more apparent, as will equivalent structures which are intended to be covered herein, with the teaching of the principles of the invention in connection with the disclosure of the preferred embodiments in the specification, claims and drawings, in which: